Resistance unit



Dec. 25, 1928.

C. DANTSIZEN RES ISTANCE UNIT Filed April 5, 1926 Figi.

Inve ntor: ChritLan DrtSLzQn. D 9 211;. .M

Patented Dec. 25, 1928.

UNITED STATES PATENT OFFICE.

CHBISTIAN'DANTSIZEN, OF SCHENECTADY, NEW YORK, ASSIGNOB T0 GENERAL ELEC-TBIC COMPANY, A CORPORATION 0F NEW YORK.

RESISTAN CE UNIT.

Application tiled April 5, 1926. Serial No. 99,778.

The present invention relates to conductors of high resistivity and moreparticularly to such conductors which are commonly emloyed inconnectionxzith vacuum tubes and known as grid leaks. Resistanceelements of this type have been made by drawing lines on paper, bspraying or painting porcelain or glass Wit ra hite and by various otherwell known met o s. Such resistances, however, usually have a seriousdisadvantage in that they vary in conductivity from time to time. Thepaper resistor, for example, is somewhat unstable, due to the fact thatthe cellulose fibers are hygroscopic or aiected by light, and in thevery slight movements of the resistor unit the la er of conductingmaterial is easily disturbe and its conductivity there? by chan d.Likewise, when resistance units are ma e by spraying or painting, it isdifiicult to obtain uniformity in the value of the resistance.

In accordance with my invention, the resistor comprises an anhydrousmaterial such as a lass rod having an etched surface, and provided atthe end portions thereof with a ayer of conducting material. Lines aredrawn on the etched surface of the glass rod and from end to end thereofwith a carbon pencil until enough carbon has been rubbed on to theroughened surface of the glass to provide a resistance element havingthe de-V sired conductivity. Resistance elements constructed in thismanner are practically constant in value and remain so throughout thelife ofmthe f The accompanying drawing illustrates in Fig. 1 a glass rodfrom which sections may be cut to provide the resistance units; Fig. 2is a perspective view illustrating the method of applying a conductingsurface to the glass rod; while Fig. 3 is a cross sectional view i1-lustrating the completed resistor unit.

In carr ing my invention into effect, a glass or other suitableinsulator rod 1 having a diameter of approximatel one-eighth inch is died into a solution o acid ammonium fluori e for a period ofapproximately 30 seconds in order to etch or roughen the surface of therod. The rod is then Washed and dried, and cut into suitable lengths 2,as indicated in Fig. 1. Conductors 3 and 4, which ma be made of 20 milsDumet wire, are then sea ed into the opposite. ends of each rod 2 andthe ends of the` rod ofthe adjacent end portions of the conductorsaregiven surface conducting coatings, asindicated at 5 and 6. The `coatingsmay comprise, for example, a graphite composition known as aquadag, andIunderstand this term to desi ate suspensions of graphite of colloidaleness in water. Coatin s 5 and 6 are of relatively high conductivity.

The rod 2 is now supported between clips, as indicated at 7 and 8 inFig. 2. A sourcevof energy, such as a batte and a milliammeter, neitherof whichare s own on the drawing, are then connected in series with thewires 3 and 4. AWhile thus connected a graphite or carbon pencil 9 isdrawn from end to end of the etched glass rod 2 until suilcientconducting material has been rubbed on to the roughened surface of theglassto give a milliammeter reading corresponding to the quotient of theapplied voltage and the desired resistance. The resistance element isthen sealed into a glass tubeor container 10, as

- indicated in Fig. 3.

In`tl`ie use of grid leaks for radio sets, it is important that vtheresistance element show as little high frequency variation as possible.This property is particularly desirable bef cause variations in theresistance ofthe grid leak are transmitted through the detector andamplified by the succeeding amplifying tubes thus giving rise toscratching or distortion in the resulting signal. I have found bynumerous tests that the type of grid leak which I have described showslittle or no high fre"- quency variations and that, as a result, thereis practically no distortion n received signals arising from the use ofthis form of resistant element.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A method of constructing a resistance unit which comprises etchingthe surface of a rod of vitreous material, sealing conductors into theends of the rod, ap lying a conducting coating to a ortion oi) saidconductors and to the ends o said rod, and drawing one or moreconductinglines on the roughened vitreous surface to electrically connect saidconducting coatings.

2. A conductor comprising a rod of vitreous material having a roughenedsurface, a pair of wires sealed into o posite ends of the rod, the endsof said rod eing provided with a .surface layer of conducting materialin contact with said wires, said roughened surface -being -provided witha deposit of conducting material connecting said surface layer.

3. A conductor comprising a lass rod having an etched surface, a pair owires sealed into opposite ends of the rod, a surface layer ofconducting material on each end of said rod and in contact with saidwires, the etched surface of the rod being provided with one or moreconducting lines connecting said sur- 10 face layers.

4. The method of constructing a resistance Legame unit,` which com risesroughening the sur- 'face of a rod o vitreous material, sealing`conductors into the ends of the rod, applying a conducting coating to aportion of said conductors and to the-ends of said rod, and drawing oneor more conducting .lines on the roughened vitreous surface toelectricallyl connect said conducting coatings.

Inwitness whereof, I Ahave hereunto set. 20

my hand this 2nd day of April, 1926.

CHRISTIAN DANTSIZEN.-

